The Eagle Plain, located in the northeastern Yukon Territory, Canada, forms a northern 19 segment of the Cretaceous Western Interior Sea. Its preserved mid-Cretaceous strata (Whitestone 20 River
Formation and Eagle Plain Group) document an active structural regime, sea-level 21 fluctuations, paleoecosystem changes and the paleogeographic evolution south of the gateway to 22 the Polar Sea. This study integrates foraminiferal assemblages
recovered from two wells (Molar 23 P-34 and Ellen C-24) and one Late Albian bentonite age with well log signatures and previously 24 established outcrop data. The emerging biostratigraphic framework correlates well and with the 25 fauna observed in
outcrops. Three biostratigraphic zones are recognized allowing for regional 26 correlations; the Early Albian Gaudryina tailleuri Zone, the Middle to early Late Albian 27 Gaudryina canadensis Zone, and the latest Albian Miliammina manitobensis Zone.
A new 28 206Pb/238U age of 105.5 ± 1 Ma places the upper Whitestone River Formation into the Late 29 Albian. Foraminiferal morphogroups and their relative proportions allow for paleoenvironmental 30 reconstruction, including oxygen and nutrient
conditions. The Ellen well represents a fully 31 marine, well oxygenated proximal shelf setting during the lower to early Late Albian Whitestone 32 River Formation. The Molar well represents a deep water, offshore setting with increased 33
accommodation space marked by an increase in tubular suspension feeders, demonstrating a 34 northwestward deepening of the basin. Foraminiferal assemblages of the Albian Whitestone 35 River Formation reflect the widely recognized depositional cycles
of the Western Interior Sea 36 (Moosebar, Hulcross, Joli Fou and Mowry seas). During Albian time the northern gateway 37 between the Polar and Western Interior seas was widely inundated, constrasting an either 38 shortlived closure or severely
restricted phase during the Albian/Cenomanian boundary interval.

Summary

(Plain Language Summary, not published)This paper provides an analysis of fossil assemblages (forams) from sedimentary rocks that formed part of the Cretaceous western Interior seaway in
northeastern Yukon territory, The data and interpretations provide information on the setting and regional correlation of these strata with units of similar age in the Arctic and Western Canada sedimentary basin. An age is reported for a volcanic ash
layer that calibrate the fossil assemblages. The paper provides a better understanding of Cretaceous sedimentary basins of western and northern Canada and their petroleum systems.